Question

Create a script (bash preferably) that automates the setup of a user in ubuntu

Answer 1

The script is written below, I have created and tested it on my Ubuntu system only, but it will work on any modern Linux Distros including Redhat and its flavors.

#!/bin/bash
  

# The script should run by the root user
# Because the useradd command to add a user
# requires root permission.

read -p "Please enter username you wish to add to the system:- " user

# Need to see if the user is already present in the system
# For this, we can easily see with the id command to find out
# if the user exists or not; exit if yes.
# The command below discards the output on the console.

if id -u $user > /dev/null 2>&1; then
echo "The user is already present in the system, please try again with a different username"
exit 1
else
# User is new to the system, prompt for the password
read -s -p "Please enter password:- " pass

# Now we are good to add the user in the system.
# But, before that we need to encrypt the password
# As useradd manual says, the password has to be
# provided in encrypted form, as returned by crypt() method.
# We are using a small perl script to facilitate this.
# We can use Python and normal openssl as well, whatever
# we are comfortable with, the only thing to make sure is
# that we should use crypt() method as that's mandatory.
encryptedPass=$(perl -e 'print crypt($ARGV[0], "password")' $pass)

# We now have both username and the password for the new user
# will use useradd command to add it in the system with below options:
# -m => the user will be having a home directory /home/$user
# -s => the shell that we want the user to have, we are using bash for example
# -p => for providing the encrypted password we just created in the above step
useradd -m -s /bin/bash -p $encryptedPass $user

echo "User has been successfully added. Try logging in with su - <newUsername>..."
fi

# script finishes here ===============================================

I am including the actual IDE screenshot as well to highlight the commands used in the above script. Please take a look.

Running the script:

We are running the script as root user hence using "sudo ./a.sh". a.sh is our script.

once the testuser is successfully added, we are testing that user by logging in with it using "su - testuser". You will notice the id shows current testuser, pwd shows its home directory and the terminal shows "testuser@" which means the user is logged in now.

Now, we return back to the previous user's session and try to add the existing user to test out negative testcase. We give the same username "testuser" and it rejects it.

From the /etc/shadow file, we can see the testuser is listed in that file and its encrypted password is also there.

From the /etc/passwd file, we can also see that the testuser is now listed which confirms the user setup.

I hope the script works for you all fine, if you have any questions, please let me know and I will glad to clarify/assist.

Thanks for asking :)